The service engineers have replaced the viscosity controller and the temperature and flow controllers of a high fuel oil heating system. The system was Gekakonus build, with the characteristic red burner motor and the red burner cover. The system was controlled by various switch panels, with outdated electric controllers. The existing controllers were replaced by I.S.S. build electric viscosity, temperature and flow controllers. These controllers are made primarily to replace Wiesloch and Aalborg electric controllers, but can also be used to replace other types of controllers. The old viscosity controller in this system was made by VAF Instruments and could be replaced by one of the I.S.S. electric controllers.